Bent plywood



Aug. 30,1938. A Q R OWENS 2,128,783

BENT PLYWOOD Filed March 22, '1937 Patented Aug. 30, 1938 My present invention relates to bent plywood which may be produced according to the method disclosed in my application iiled October 27, 1936, under Serial No.' 107,810, now Patent No. 2,074,854, issued March 23, 1937. It is commonly desired to produce a bend in plywood so as to form a round corner which is suitable for use, in trim, cabinets, furniture pieces of Various kinds, etc. By the improvements of this invention I am enabled to provide a bent structure which is ample in strength, which will retain its shape and appearance indefinitely, and which maybe produced with little or no forces of compression to be overcome.

As illustrative of the bent plywood and the method employed, reference may be had to the accompanying drawing, wherein:

Figure 1 is an edge view of a plywood board in the rst stage of its preparation for the bending operation;

Fig. 2 which is a similar View shows the board in the next stage of its preparation;

Fig. 3 which is an edge view shows the board with the bend completed;

Fig. 4 shows akmechanism suitable Vfor producing the desired bend in the board;

Fig. 5 which is a fragmentary longitudinal section on an enlarged scale shows the board as it appears in the first stage of its preparation for the bending operation;

Fig. 6 which is a similar View shows the board the second stage of its preparation; and

Figs. 7 and 8 are Views corresponding generally to Figs. 5 and 6, respectively, showing a board of ve plies instead of four plies as is elsewhere illustrated.

The board now to be described may be of plywood with a core a of relatively soft wood to one face of which is adhered a cross bandV b` upon which is mounted a veneer face c. Applied tothe rear face of the core is a back d. The several plies are arranged preferably with grains crosswise of each other and are united in the usual manner as by layers of glue e.

To prepare the board for the bending operation the back is rst loosened from the core between certain imaginary lines and y which dene the region of the board where a bend is to be made. The back is then slitted between these lines or along one of them, the line a: for example, a sufficient strip-like part of its body adjacent the line of severance being removed 'to leave a substantial gap which interrupts the continuity of the back. The two spaced edges of the back which denne this gap are designated as f and g. It

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ifcago, Ill., assigner to Wellsl y; Chicago, lll., a corporasNroFFic E Applicaties Maranza, 1937,l serial Nd. 132,191 1 Claim. (credi-'sei' will be understood that the freed portion of the back, including the gap between its facing edges, extends between opposite edges of the board. As shown in Figs. 2 and 6, the back is thereupon left unsupported except in the regions beyond the 5 lines and y.

Glue is now applied between the back and core, and, while still unset, a bending force is applied to the board in the region between the lines a: and y. This may be done conveniently with the 10 aid of a die F and a form R. Throughout that portion of the board which is thereupon bent the glue is unset at the time, permitting the back to slide freely, as required, so as to obviate compression. The initial width of the gap between l5 the back ends J" and g may correspond generally with the distance which one or both of these ends of the back will be required to move while taking up a new position during the bending operation.

As a result, the gap will be substantially closed so as to restore continuity to the back when the bend is completed (see Fig. 3). The bending force is maintained a suflicient time to allow the glue to set whereupon the band becomes permanent and the board lmay be removed. The back which is the inside ply in the bentboard will resist unbending of the board due to its exerting a tension force which counterbalances that of the plies to the outside of the bend.

A bend of the kind described may be produced from a board having three, four, five or more plies. A board of four plies has been illustrated and -described by way of example. In Figs. 7 and 8 I-have shown a five ply board having a second cross band h disposed between the back and core. In preparation for the bend which is to be made it will be desirable, although perhaps not necessary, to produce an interruption in the band as well as the back (see Fig. 8). In such case the cross band is -disconnected from the core between the lines a: and y which dene the region of the bend, and the back is also disconnected from the cross band whereby, during the bending operation, each of these plies may slide independently, the band upon the core and back, and the back upon the band. At the completion of the bend, these two plies will have substantially closed the gap between their ends f and y.

The essence of my invention resides in freeing one or more plies upon the inner side of the board where compressive forces are developed during a bending operation, in cutting out a narrow section of such ply or plies so as to pro-duce a gap or Vinterruption lengthwise thereof, in applying glue between such ply or plies and the adjacent is still unset, a bending force which will produce a sliding movement of the freed ply or plies, thereby avoiding compression thereof, and in maintaining the bending force until the glue has set. These several steps are requisite with a conventional plywood as now produced, but obviously, if the back be initially applied so that it is already freed in part and/0r slitted to provide a gap, then these preliminary steps may be omitted when carrying out the remaining steps of this process.

The number of plies at the inner side of the board which are to be loosened in preparation for bending will depend in large part upon the character and thickness of the board, it being important that so much of the inner board face as would ordinarily be subjected to a compressive force while undergoing bending be loosened andr 2,128,73 surface of the board, in applying, while the glue cut away to induce a sliding action. n perform ing the bend any of the usual expedients may be employed, such as steam, to facilitate shaping of the wood, and heat to accelerate setting of the glue, etc. A resinous glue, either sheet or liquid, will ordinarily be found satisfactory.

I claim:

A bent board of plywood having its several plies united and extended continuously throughout the bend, the ply to the inside of the bend having l0 a transversely extending section removed therefrom at a point Within the bend and having its innerrsurface united throughout its extent to the adjacent bent ply with its opposed edges in abutting relation, whereby to reduce the circumferential length of the inner ply without the setting up of a'compressive force therein.

ORVILLE R. OWENS. 

